This application relates generally to devices and methods for implanting an intraocular pressure (IOP) sensor within an eye of a patient, particularly by injecting the IOP sensor device within a patient's eye for monitoring and management of glaucoma treatment.
Glaucoma is a condition resulting in increased pressure within the eye that eventually leads to damage of the optic nerve that transmits images to the brain, which results in gradual vision loss. The increased pressure within the eye causes a loss of retinal ganglion cells in a characteristic pattern of optic neuropathy. A patient suffering from glaucoma typically experiences a build-up of aqueous fluid which increases the pressure inside the eye (i.e. intraocular pressure). Elevated IOP is one of the primary risk factors for developing glaucoma, which must be carefully monitored and controlled in treating glaucoma. As retinal ganglion cells are damaged by glaucoma, the visual signals from at least a portion of visual field are no longer reported to the brain, forming blind spots or scotomas. As glaucoma progresses and increasingly damages more nerve tissue in the optic nerve, vision loss continues as the scotomas increase in size and/or number. Failure to properly treat glaucoma and to reduce and monitor the IOP may cause irreversible vision loss. Untreated glaucoma, which affects one in 200 people under the age of fifty and 10% of those over the age of 80, is the second leading cause of blindness worldwide. As of 2012, about 60 million people suffer from glaucoma world-wide and it is estimated that, by 2020, about 80 million people will suffer from glaucoma. In addition, since a high percentage of people are over the age of 75 years old, and as the world-population ages and life-spans increase, it is expected that glaucoma patient populations will continue to increase.
IOP in a healthy human eye is generally between 10 mmHg and 20 mmHg. Glaucoma causes substantial increase in and/or variation in IOP than that experienced in a healthy eye. The IOP is determined largely by the amount of aqueous fluid entering and exiting the eye. Aqueous fluid is produced by the ciliary body to supply the lens and cornea with nutrients and carry away waste products. Normally, aqueous fluid flows between the iris and the lens, through the pupil and to the drainage angle before exiting the eye through a tissue called the trabecular meshwork in the drainage angle, including the schlemm's canal. If the aqueous fluid is produced at a rate faster than it drains, then the intraocular pressure will rise. An elevated intraocular pressure is associated with two major types of glaucoma: open-angle glaucoma and closed-angle glaucoma. In open-angle glaucoma, the drainage angle between the cornea and the iris is open and allows the aqueous fluid of the eye to reach the trabecular meshwork, but abnormalities in the trabecular meshwork reduce the outflow of aqueous fluid from the eye. In closed-angle glaucoma, obstructions within the trabecular meshwork prevent the aqueous fluid from draining properly out of the eye.
While the progression of glaucoma can be substantially halted in many patients using a variety of treatments, for example, medicines, prescription eye drops, shunts, and surgical procedures, failure to properly diagnose and/or monitor the IOP of a patient can drastically reduce the effectiveness of available treatments. Currently, glaucoma monitoring often uses infrequent IOP measurements obtained by a physician at a medical facility. For example, a typical patient may have their IOP measured on average four to six times per year by non-invasive techniques, such as tonometry. While tonometry techniques are generally low cost, easy, and non-invasive, a number of different types of errors can significantly reduce the accuracy of this diagnostic tool and as such potentially result in inappropriate diagnosis and/or ineffective follow-up medical treatment.
For example, at least some of these non-invasive clinical techniques may not detect elevated IOP levels (e.g., pressure spikes) as only a single point measurement is taken during an eye exam. Failure to continuously and/or frequently monitor IOP levels outside the eye clinic (e.g., more than four to six measurements per year) may lead to inaccurate detection of the patient's real IOP profile (e.g., real IOP may be higher or lower than measured IOP). Non-invasive measurements in some instances lack accuracy as these devices measure pressure of the eye with an external sensor that provides an indirect measurement of the actual pressure inside the eye and are unable to capture the dynamic state of the disease in which there is a continuously changing IOP at low and high frequency rates with up to 12,000 spikes per hour. For example, factors that affect accuracy may include failure to account for anatomical differences, such as a patient's cornea thickness, scleral rigidity, or conical curvature, variances due to operator's use or technique, physiological influences, such as caffeine or alcohol use, or prior refractive surgery that may affect a patient's IOP, etc. Hence, the indirect IOP measurements from such non-invasive devices may differ from the actual IOP inside the eye (e.g., overestimated or underestimated) which may lead to inappropriate diagnosis and/or follow-up treatment. Further, it is often inconvenient and impractical for patients to visit the eye clinic on a strict regular schedule for repeated IOP measurements.
Although implantable IOP devices have been proposed for direct IOP measurements on a daily basis, these first generation implants may also suffer from several drawbacks which in turn may result in indirect and/or inaccurate measurement of IOP and inappropriate medical treatment of glaucoma. For example, the IOP devices may be too large or bulky in dimension, size or shape to be safely and effectively placed entirely within a desired location or structure of the eye for direct measurement of IOP. Further, some devices may be extremely invasive, requiring major surgery for implantation and/or complicated positioning of multiple components which are each implanted in different structures or areas of the eye, which unnecessarily increases patient risk and/or injury and total healthcare costs.
Further, some IOP implantable devices may utilize pressure ports which are susceptible to sensing inaccuracies or require direct implantation within certain anatomical locations, such as the anterior chamber, posterior chamber, suprachoroidal space, or cornea of the eye which may lead to unanticipated complications. Also, some of these devices may not be well suited for chronic implantation due to IOP implant design issues of water ingress and/or thermal stress (e.g., associated with polymer packaging), which in turn precludes continuous monitoring of IOP. Such proposed flexible sensors also have issued of degraded stability. In some instances, some IOP devices also suffer from poor calibration and/or monitoring is not adjustable so as to further result in inaccurate IOP detection levels.
Accordingly, it would be desirable to provide improved implant devices and methods of implantation that overcome at least some the above mentioned shortcomings. In particular, it would be desirable to develop ultra-miniature implantable IOP devices that accurately, continuously, and adjustably monitor IOP levels. Ideally, such devices should directly measure IOP pressure levels and can be safely and effectively implanted entirely within a desired location within the eye quickly and easily in an outpatient environment, such as the physician's office, without invasive major surgery. Such devices should further allow for chronic implantation so as to provide long-term stable and continuous IOP measurement profiles for appropriate diagnosis and follow-up therapy. In addition, there exists a need for improved methods of implantation for such devices within the eye that do not require surgical intervention and avoid damage to the sensitive structures of the eye.